1. Field of the Invention
The present invention relates to a connector for flexible pipes, particularly for use in cooling or air-conditioning systems for motor vehicles, of the type comprising a hollow main body including a coupling element for a flexible pipe, the coupling element having at least one gripping tooth for cooperating with clamping means to grip the flexible pipe when the connector is in the condition of use.
2. Description of the Related Art
An example of a connector of the known type indicated above is illustrated and generally indicated 1 in the appended FIG. 1. This connector has a tubular coupling element 2 on which two ramp-like, annular teeth 3 and two pairs of sealing collars 4 are formed integrally. In use, the end of a flexible pipe 5 is fitted and clamped on the coupling element 2 by the plastic deformation of a collar 6 which, in the example of FIG. 1, is constituted by a pair of bands 7 connected in a tandem configuration by a transverse plate 8.
A disadvantage of known connectors is that the characteristics of the seal between the pipe and the coupling element for preventing the escape or leakage of the operating fluid are not entirely satisfactory when the fluid has small molecular dimensions.
This problem is accentuated by the fact that, in order to reduce the permeability of the pipes to fluids of this type, flexible pipes having an internal sheathing of polyamide material, particularly nylon, are often used.
As is known, polyamide materials generally have poor flexibility characteristics and hence a poor ability to adapt to the gripping teeth of the coupling elements of the connectors, particularly to ramp-like annular teeth, with the risk of imperfect adhesion between the inside wall of the pipe and the coupling element, although only in a localized region.
Another disadvantage of known connectors connected to flexible pipes having an internal polyamide sheathing is caused by the difference between the coefficient of thermal expansion of the sheathing and that of the metal of which the connector, including any sealing collars, is made. This difference between the coefficients of thermal expansion means that the coupling element of the connector tends to contract radially to a greater extent or more rapidly than the flexible pipe as a result of abrupt reductions in the running temperature, with the consequent danger of the fluid leaking.
The object of the present invention is to overcome the aforesaid problems by means of a connector of the type indicated in the introduction to the present description, characterized in that it comprises at least one sealing ring having a substantially cylindrical inside wall and a shaped outside wall, the sealing ring exhibiting resilient behaviour in a radial direction and being compressible radially, when the connector is in the condition of use, by the flexible pipe which is fitted and clamped on the coupling element by the clamping means.
An advantage of the connector according to the present invention is that its fluidtightness is ensured even in the presence of any geometrical defects or surface faults either of the coupling element or of the passage inside the flexible pipe, reducing production costs by virtue of the lower incidence of rejects. In fact, by virtue of the sealing ring, the fluidtightness of the connector is not affected by lack of adhesion of the flexible pipe to the coupling element in a localized region thereof.
Another advantage of the connector according to the present invention results from the fact that, even in difficult conditions of use, it is not necessary to increase the force with which the flexible pipe is clamped onto the connector to ensure a satisfactory seal and the risk of undesired deformation or breakage of the coupling element or of the internal polyamide sheathing, when it is present, is thus reduced.
If the connector according to the present invention is used with a flexible pipe having an internal polyamide sheathing, another advantage is achieved; in this case, the friction between the sealing ring and the polyamide sheathing, which is undoubtedly greater than the friction which normally arises between the sheathing and the metal of known connectors, effectively stops any relative rotation between the connector and the pipe when clamping has been effected. The risk of fluid leaking or escaping is thus undoubtedly reduced.
According to another characteristic of the present invention, the sealing ring is housed with a resilient forced fit in an annular recess in the coupling element.
An advantage resulting from this characteristic is that the fitting of the sealing ring on the coupling element is quick and easy to do and can easily be automated. Moreover, the longitudinal position of the sealing ring on the coupling element is defined at the design stage so as to optimize the sealing characteristics of a certain model of connector according to the type of clamping means used for the flexible pipe.
According to a further characteristic of the connector according to the present invention, the outside wall of the sealing ring is substantially arcuate in shape.
Two advantages result from this further characteristic; on the one hand, it prevents the sealing ring from being displaced or rolled up when the flexible pipe is fitted on the coupling element since the convex shape of its outside wall favours the sliding of the flexible pipe thereon, as long as it is not clamped; on the other hand, the compression force exerted on the sealing ring radially by the flexible pipe clamped onto the coupling element is preferably discharged uniformly onto the sides of the sealing ring, bringing about, amongst other things, a more progressive resilient action and a greater useful travel.